I tried the WIFI scan using WICED 3.7.0-3 at my end using BCM4343W avnet kit and I did not see any issue. All the APs are being scanned same as previous versions. I tried on WICED 3.7.0 and am seeing the same APs.

I wasn't aware custom designs were not supported here. Can you direct me to a route to help support issues on here?

I realized that the networking worker thread had a very small (16 position) queue. the scan, being well over 16 APs, overflowed this queue and the "success" message was rejected. I've increased the size of the queue and this now works 100%.